Hormone changes, such as elevated prolactin and low thyroid levels, might cause a woman to stop having a period, according to Penn State Hershey. Eating disorders, such as bulimia nervosa and anorexia, may prevent ovulation and stop menstruation, states the Global Library of Women's Medicine. In addition, certain medications might also stop ovulation and menstruation, including some antipsychotics, morphine and tricyclic antidepressants. In addition, some women under the age of 40 might experience premature ovarian failure, which causes early menopause and stops menstruation, states Penn State Hershey.